(1) Field of the Invention
The present invention relates generally to mechanical erectors and more particularly to an antenna erector for a towed buoyant cable that uses a shape memory alloy to raise an antenna.
(2) Description of the Prior Art
Communication with and between underwater vehicles currently makes use of towed buoyant cables that are equipped to transmit and receive electromagnetic radio waves. Since seawater is electrically conducting, penetration of the radio frequency electromagnetic waves below the surface of the water is limited. Furthermore, as the frequency of the electromagnetic waves increases, penetration depth of the electromagnetic waves decreases. Accordingly, the cables are made buoyant to maintain the transmit/receive components at the surface of the water. Unfortunately, the cables frequently experience wave "wash over" during transmission/reception. Wave wash over essentially increases the amount of water over the cable which may interrupt communications. In addition, underwater vehicles often need to communicate when traveling at speeds that generate hydrodynamic forces that may pull the towed cable below the surface of the water.
One way to counter these problems is to mount an antenna on the towed buoyant cable. The height of the antenna would be such that it would extend from the surface of the water during wash over and when the underwater vehicle was traveling fast enough to pull the towed cable below the surface. However, an erected antenna would not survive many of the operational maneuvers of underwater vehicles. Furthermore, maintaining an antenna above the surface of the water is contrary to the notion of (underwater) stealth vehicles.